Tree limbing operations and tree limbing aspects of brush cutting operations are difficult to carry out when the limbs are relatively large and/or are relatively inaccessible. Limbs that are high up on a tree can be cut by hand by an operator who climbs the tree and uses a hand-held chain saw to cut the limbs. This type of operation is potentially dangerous and, thus, requires a high level of skill. In addition, it is time consuming and expensive to carry out. Some types of boom-mounted cutting heads are capable or removing limbs high up on a tree. However, known types of boom-mounted cutting heads have the serious limitation of being unable to cut limbs unless the side of the tree from which the limbs project can be approached directly by the machine which carries the boom structure. In situations in which surrounding trees or other obstructions prevent direct approach, the limbs must be cut by hand.
U.S. Pat. No. 2,815,048, granted Dec. 3, 1957, to G. Davis, discloses a mobile brush cutting machine having an articulated boom and a tool supporting head mounted on the outer end of the boom. The head includes a base on which a chain saw is mounted. The angle of the head relative to the boom is adjustable by means of a circular series of holes that selectively receive fasteners to allow adjustment about the boom axis. A series of arcuately arranged anchor holes similarly allow adjustment about a horizontal axis defined by the boom/head connection. The relative angular orientation does not change during the operation of the machine but, rather, remains the same until the pin connections are detached and a different set of holes is selected. The operator controls the position of the chain saw by pivoting the boom and extending and retracting the outer telescopic arm of the boom.
U.S. Pat. No. 3,494,389, granted Feb. 10, 1970, to J. L. Thibodeau, discloses apparatus for grasping, slashing (cutting to length), and loading felled timber. The apparatus includes a main boom, a knuckle boom attached to the main boom, a hoist bar attached to the outer end of the knuckle boom, and a clamp frame suspended from the bar. Jaws for gripping the timber are carried by the clamp frame. The manner in which the clamp frame is mounted maintains the jaws perpendicular to the ground. A hydraulically powered ring saw or chain saw is mounted on the frame. In each embodiment, the saw is movably mounted to achieve a cutting motion of the saw. The ring saw moves vertically to cut the timber. The chain saw is pivoted about a horizontal axis.
U.S. Pat. No. 4,281,693, granted Aug. 4, 1981, to D. C. Moulson, discloses tree felling apparatus that includes an articulated boom mounted on a tracked vehicle and a felling head mounted on the outer end of the boom. Moulson discusses prior art feller heads with chain saws movably mounted to pivot or translate while cutting. He states that the prior art feller heads present the problem of requiring too large a size of the head for boom mounting in order to accommodate the degree of movement of the chain saw required to sever larger trees. In the Moulson device, tree trunks are received into a recess on the head and secured by grippers. A chain saw motor is mounted on an arcuate track and is moved along the track to move the chain saw across the recess and cut a tree trunk gripped therein.
U.S. Pat. No. 3,343,575, granted Sep. 26, 1967, to T. E. Trout, discloses a rotary saw attachment for a backhoe. The attachment is pivotably mounted on an outer boom and carries a rotary disk saw that is pivotable about the axis of the attachment.
U.S. Pat. No. 4,802,327, granted Feb. 7, 1989, to C. A. Roberts, discloses a mower attachment for tractors that has a rotary disk cutter with a peripheral groove in which a cutting chain is mounted. U.S. Pat. No. 4,769,977, granted Sep. 13, 1988, to the present applicant, discloses a brush cutter having a head with a disk rotary cutter that is capable of limbing trees.